Interface FlutterPlugin

A Flutter plugin allows Flutter developers to interact with a host platform, e.g., Android and iOS, via Dart code. It includes platform code, as well as Dart code. A plugin author is responsible for setting up an appropriate MethodChannel to communicate between platform code and Dart code.

A Flutter plugin has a lifecycle. First, a developer must add a FlutterPlugin to an instance of FlutterEngine. To do this, obtain a PluginRegistry with FlutterEngine.getPlugins(), then call PluginRegistry.add(FlutterPlugin), passing the instance of the Flutter plugin. During the call to PluginRegistry.add(FlutterPlugin), the FlutterEngine will invoke onAttachedToEngine(FlutterPluginBinding) on the given FlutterPlugin. If the FlutterPlugin is removed from the FlutterEngine via PluginRegistry.remove(Class), or if the FlutterEngine is destroyed, the FlutterEngine will invoke onDetachedFromEngine(FlutterPluginBinding) on the given FlutterPlugin.

Once a FlutterPlugin is attached to a FlutterEngine, the plugin's code is permitted to access and invoke methods on resources within the FlutterPlugin.FlutterPluginBinding that the FlutterEngine gave to the FlutterPlugin in onAttachedToEngine(FlutterPluginBinding). This includes, for example, the application Context for the running app.

The FlutterPlugin.FlutterPluginBinding provided in onAttachedToEngine(FlutterPluginBinding) is no longer valid after the execution of onDetachedFromEngine(FlutterPluginBinding). Do not access any properties of the FlutterPlugin.FlutterPluginBinding after the completion of onDetachedFromEngine(FlutterPluginBinding).

To register a MethodChannel, obtain a BinaryMessenger via the FlutterPlugin.FlutterPluginBinding.

An Android Flutter plugin may require access to app resources or other artifacts that can only be retrieved through a Context. Developers can access the application context via FlutterPlugin.FlutterPluginBinding.getApplicationContext().

Some plugins may require access to the Activity that is displaying a Flutter experience, or may need to react to Activity lifecycle events, e.g., onCreate(), onStart(), onResume(), onPause(), onStop(), onDestroy(). Any such plugin should implement ActivityAware in addition to implementing FlutterPlugin. ActivityAware provides callback hooks that expose access to an associated Activity and its Lifecycle. All plugins must respect the possibility that a Flutter experience may never be associated with an Activity, e.g., when Flutter is used for background behavior. Additionally, all plugins must respect that a Activitys may come and go over time, thus requiring plugins to cleanup resources and recreate those resources as the Activity comes and goes.